High melt flow filled propylene polymer compositions suitable for injection molding are provided. The compositions are blends of propylene impact copolymer, high melt index plastomer and mineral filler.

The present invention relates to filled propylene polymer blend compositions suitable for injection molding comprising a propylene-ethylene impact copolymer and an ethylene plastomer having melt flow rate greater than 10. The blends, and particularly visbroken blends, exhibit high flow and provide a desirable balance of impact properties and dimensional stability.
Two phase propylene copolymer resins comprised of an intimate mixture of a continuous phase of crystalline propylene homopolymer and dispersed rubbery phase of ethylene-propylene copolymer are well known and widely used for numerous applications. While these so-called impact polypropylene products can be produced by melt compounding the individual polymer components, existing multi-reactor technology makes it possible to directly produce these products. This is conveniently accomplished by polymerizing propylene in a first reactor and discharging the polypropylene homopolymer from the first reactor into a secondary reactor where propylene and ethylene are copolymerized in the presence of the homopolymer. Gas-phase polymerizations of this type are described in the article by Ross, et al. al., xe2x80x9cAn Improved Gas-Phase Polypropylene Process.xe2x80x9d Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, pp. 149-154. This gas-phase technology has been extended to products containing significantly higher rubber/elastomer contents which are referred to as in-situ thermoplastic polyolefins (TPOs).
The high rubber content PP-EPR materials produced by these in-reactor processes are increasingly being used by the automotive industry for the manufacture of injection molded large parts such as bumpers, body side mouldings and the like. Primary requirements for materials used for these applications are good impact and high dimensional stability, i.e., low coefficient of linear thermal expansion (CLTE). The need for bumper materials having reduced expansion or xe2x80x9cO-gapxe2x80x9d and the ability to significantly improve the expansion coefficient using mineral fillers is discussed by E. Seitl, et al., Kunstoffe Plast Europe, August 1994, pp. 50-53. The reference further notes that the expansion coefficient also influences the shrinkage. Shrinkage is an important consideration in the injection molding process since tools/molds are designed for a certain shrink requirement.
Ethylene-olefin elastomeric copolymers (plastomers) are known to be useful modifiers for polypropylene impact copolymers. The addition of plastomers makes it possible to obtain blends with enhanced properties, such as improved low temperature ductility. This latter feature is important since most manufacturer specifications now also have ductile-brittle failure mode requirements in addition to low temperature (xe2x88x9230xc2x0 C. or xe2x88x9240xc2x0 C.) impact requirements. For high flow injection molding polypropylene compositions there also are certain melt flow rate (MFR) requirements if acceptable fabrication is to be achieved.
U.S. Pat. No. 6,399,707 discloses polypropylene impact copolymer blends with low melt index (MI) plastomers, i.e., plastomers with MIs from 0.8 to 10 g/10 min and, more preferably, 0.8 to 3.5 g/10 min. The reference points out that while higher MFR ( greater than 15 g/10 min) materials are desirable for injection molding, it is difficult to achieve the low temperature ductility and impact properties required by the automotive industry with such high MFR resins. For this reason resin blends having MRFs less than 15 g/10 min are used.
It would be highly advantageous if polypropylene impact copolymer/plastomer blends having higher MFRs with acceptable impact and low temperature ductility were available. These and other benefits are achieved with the improved compositions of the invention which are described in detail to follow.
The present invention provides propylene polymer compositions suitable for injection molding. More specifically, the compositions are blends of ethylene-propylene impact copolymers, ethylene-olefin plastomers and mineral fillers. They are characterized by having high flow and a desirable balance of impact and dimensional properties.
The compositions are blends comprised of 45 to 90 weight percent (wt. %), based on the total composition, propylene-ethylene copolymer comprised of crystalline and amorphous phases, said copolymer having an ethylene content from 5 to 25 wt. % and MFR from 10 to 60 g/10 min; 5 to 35 wt. %, based on the total composition, ethylene-C4-8 xcex1-olefin plastomer, said plastomer having a density less than 0.92 g/cm3 and MI from 12 to 50 g/10 min; and 5 to 40 wt. %, based on the total composition, mineral filler. MFRs of the compositions will range from 20 to 60 g/10 min and, more preferably, are from 25 to 50 g/10 min. In one highly useful embodiment of the invention, the above-described MFRs are achieved by visbreaking lower MFR blends of the components. Typically blends which are visbroken have initial MFRs less than 20 g/10 min. Visbreaking is particularly advantageous when MFRs of the initial blend are 15 g/10 min or less.
Preferably the improved compositions of the invention are talc-filled and contain 0.01 to 1 wt. % blending aid. Ethylene-octene-1 copolymers having densities from 0.86 to 0.90 g/cm3 and MIs from 20 to 40 g/10 min are particularly useful plastomers for the inventive blends.
The propylene polymer compositions of the invention are high flow blends of impact copolymer, plastomer and filler useful for injection molding applications. The high flow compositions are particularly suitable for the manufacture of injection molded parts which require high impact, low temperature ductility and dimensional stability, such as exterior automobile components. It is generally recognized that attempting to increase flow rates of injection molding blend resins by using higher MFR propylene impact copolymers adversely affects impact resistance. On the other hand, if the amount of plastomer is increased to compensate for the impact loss, the flow rate is adversely affected.
By high flow is meant compositions, having MFRs 20 g/10 min or greater, most commonly, from 20 to 60 g/10 min. Resins having MFRs in the range 20 to 60 g/10 min are, from the standpoint of fabrication, considered to be highly suitable for use in injection molding equipment. MFRs referred to herein are determined in accordance with ASTM D 1238 at 230xc2x0 C. and 2.16 Kg load. In those instances where the MI is specified, the MI is determined using test method ASTM D 1238 at 190xc2x0 C. and 2.16 Kg load.
From the standpoint of product performance for the above-referenced automotive applications, impact properties and the ability to control expansion and contraction of the parts during production and end use are paramount. For obvious reasons performance criteria include impact strength requirements. In recent years, however, cold impact resistance of the material determined using an instrumented impact test and the type of failure mode (brittle-ductile) have become increasingly important material performance specifications for manufacturers. These test procedures will be described in more detail to follow.
Dimensional stability, as referred to herein, relates to both the expansion/contraction characteristics of the material after it is molded and the shrink characteristics of the material during fabrication. The former is determined by measuring the coefficient of linear thermal expansion in accordance with ASTM test method E 831. Shrinkage is determined by observing the difference in size of a molded plaque from the mold dimensions after the plaque has been allowed to stand, typically for 24 hours.
The ability to balance all of the aforementioned properties of an injection molding resin to achieve the optimal balance of properties, i.e. optimize each of the properties without unduly sacrificing the performance of any one property, is highly desirable. Furthermore, the ability to vary individual properties by judicious modification of the injection molding resin composition is equally advantageous. These objectives are accomplished with the blend compositions of the present invention by varying the amount and type of propylene impact copolymer and/or plastomer used and, optionally, visbreaking the filled impact copolymer/plastomer blend.
Propylene polymers used for the compositions of the present invention are propylene-ethylene copolymers comprised of crystalline (propylene homopolymer) and amorphous or rubber (ethylene-propylene copolymer) phases. Ethylene contents of the propylene-ethylene copolymers will range from 5 to 25 wt. % and, more preferably, from 6 to 22 wt. %. MFRs will range from 10 to 60 g/10 min and, more preferably, from 15 to 40 g/10 min. Ethylene-propylene rubber contents will range from about 10 to about 50 wt. %.
Useful propylene-ethylene copolymers employed for the invention, also referred to herein as impact copolymers, are known and may be obtained by physically blending a propylene homopolymer with the requisite amount of ethylene-propylene rubber. They are, however, preferably produced using gas-phase, stirred-bed polymerization processes. These processes utilize two reactors connected in series and high activity supported transition metal catalysts. In such processes, reactor-made intimate mixtures of propylene homopolymer and propylene-ethylene copolymer are produced.
More specifically for such processes, propylene is homopolymerized in a first reactor at a temperature from 50xc2x0 C. to 100xc2x0 C. and pressure from 250 psig to 650 psig utilizing a titanium catalyst and an organoaluminum cocatalyst. Preferably the temperature in the first reactor will be from 50xc2x0 C. to 90xc2x0 C. and the pressure will range from 300 psig to 450 psig. The highly isotactic homopolymer produced in the first reactor is then directly fed to a second reactor which is maintained at 25xc2x0 C. to 80xc2x0 C. and 100 psig to 500 psig where propylene and ethylene are copolymerized in the presence of the homopolymer. The amount of ethylene employed in the second reactor is sufficient to produce the copolymer with rubber-like characteristics. Polymerization in the second reactor is generally accomplished without additional catalyst; however, it may be advantageous to introduce more catalyst to the second reactor. If more catalyst is employed, it can be the same as the catalyst used in the first polymerization or different. Preferably, the second polymerization reactor is operated at 40xc2x0 C. to 70xc2x0 C. and 100 psig to 350 psig. A high activity titanium catalyst activated by contact with an organoaluminum cocatalyst is utilized for these polymerizations. The polymerizations are carried out in the substantial absence of liquid reaction medium and gas velocity within the stirred-bed is maintained below the onset of fluidization. Depending on their compositional makeup, gases can be recirculated through external heat exchanges for cooling or partially condensed. Cooled monomer is recirculated into the reactor and provides thermal control. Recirculated monomer vaporizes when it is introduced into the reactor so that polymerization occurs in the gas phase. In the preferred mode of operation, i.e., stirred, fixed-bed gas phase, the first and second reactors are fitted with spiral agitators to maintain a turbulent mechanically fluidized bed of polymer powder and prevent agglomeration.
Each reactor typically has its own control system(s) and is capable of independent operation. In the usual conduct of the process, propylene and ethylene monomers are passed through desiccant beds prior to introduction. Means are usually provided to individually meter the propylene, ethylene, hydrogen for molecular weight control, catalyst and cocatalyst. This makes it possible to more readily control and maintain the desired reactor conditions. If desired, monomer may be injected into the recirculated gas stream for introduction into the system. Residence times in both reactors are on the order of 1 to 4 hours.
The use of dual or cascading reactors for the homopolymerization and copolymerization of propylene and ethylene to produce ethylene copolymers is known. Similarly, gas-phase polymerizations utilizing stirred, fixed beds comprised of small polymer particles are also known. For additional information regarding gas-phase polymerizations and a schematic flow diagram of the process, reference may be made to the article by Ross, et al., in Ind. Eng. Chem. Prod. Res. Dev., 1985, 24, pp 149-154, which is incorporated herein by reference.
The improved compositions of the invention have 45 to 90 wt. % of the propylene-ethylene copolymer blended with the plastomer and filler. Particularly useful products are obtained when the propylene impact copolymer constitutes 55 to 75 wt. % of the injection molding composition. Weight percentages of the impact copolymer and other blend components are based on the weight of the total composition.
Combined with the propylene impact copolymer to obtain the improved blend compositions of the invention is 5 to 35 wt. % and, more preferably, 10 to 30 wt. % of a plastomer or plastomer blend. The plastomer component is an ethylene based polymer, i.e., a polymer having ethylene as the major constituent, prepared using a metallocene catalyst. Metallocene or xe2x80x9csingle sitexe2x80x9d catalysts having at least one cyclopentadienyl or analogous ligand coordinated to a transition metal cation as well as plastomers produced using such catalyst systems are known. Metallocene catalysts and polymerization processes are described in U.S. Pat. Nos. 5,017,714 and 5,324,820 which are incorporated herein by reference.
Useful plastomers for the invention are copolymers of ethylene and C4-8 xcex1-olefin comonomers. Ethylene generally comprises from about 87 to about 97.5 mole % with the xcex1-olefin comprising from about 2.5 to 13 mole % of the plastomer. The plastomers will have densities less than 0.92 g/cm3 and, more typically, from 0.86 to 0.92 g/cm3. Most preferably the plastomer densities will be from 0.86 to 0.90 g/cm3. Plastomer copolymers are described in more detail in U.S. Pat. No. 6,207,754 which is incorporated herein by reference.
The ethylene-xcex1-olefin plastomers will have MIs from 12 g/10 min up to about 50 g/10 min. In a highly useful embodiment of the invention the plastomer MI will be from 20 to 40 g/10 min. Copolymers of ethylene and butene-1, hexene-1 and octene-1 are highly useful plastomers. Such plastomers are available from commercial sources. A particularly useful plastomer with density and MI within the above-recited ranges is an ethylene-octene-1 copolymer sold under the designation EG8407 (DuPont Dow Elastomers).
The use of plastomers as modifiers to increase impact strength and lower the brittle-ductile transition temperature of propylene copolymers is known; however, plastomers heretofore used have been low MI materials. Plastomers disclosed in the prior art have typically had MIs of 10 g/10 min or below and, more commonly, from about 1 to 5 g/10 min. The use of higher MI plastomers would be considered to be undesirable based on the generally recognized view that increasing the melt flow of polypropylene blends is detrimental to impact properties.
A mineral filler is included with the impact copolymer and plastomer. The filler will constitute 5 to 40 wt. % and, more preferably, 10 to 25 wt. % of the blend composition. Any of the conventional filler materials typically used with polyolefins can be employed. Such fillers can include calcium carbonate, clay, talc, kaolinite, wollastonite, pyrophillite, magnesium hydroxide, oxides of zinc and magnesium, silica and silicates, and the like.
The use of talc fillers is highly advantageous for the compositions of the invention. Useful talcs may be untreated or surface treated in accordance with known procedures. Talc surface treatments may include treatments with silanes, fatty acids, fatty acid metal salts or the like. Filler particle sizes may vary; however, it is generally preferred to utilize fillers having average particles sizes from about 0.5 to about 10 microns. Talc having an average particle size between about 0.5 and 2.5 microns is particularly useful for formulating the compositions of the invention.
The compositions of the invention may also contain optional additives commonly used for the formulation of propylene polymer resins. These additives include but are not limited to processing aids, antioxidants, heat stabilizers, UV absorbers, dispersants, crystallization accelerators, antistatic agents, lubricants and the like. The total amount of additives used will not exceed about 5 wt. % of the composition and, most preferably, will range between about 0.01 and 2.5 wt. %.
In one highly useful embodiment of the invention, the compositions will contain 0.01 to 1 wt. % of a blending aid to facilitate uniform incorporation of the filler in the impact copolymer/plastomer polymer matrix and insure production of a homogeneous blend. Conventional blending aids can be employed for this purpose. Examples of useful blending aids include maleated polypropylenes; silanes; neoalkoxy titanates; fatty acid derivatives, such as metal soaps, amides and esters; low molecular weight aliphatic resins; and the like. Many of these additives have multiple functions and may also function as processing aids, compatibilizing agents, slip agents, lubricants, mold release agents, etc. for the resulting compositions. In one highly useful embodiment of the invention the blending agent is a blend of a fatty acid metal soap and an amide. Blending aids of this type are commercially available. One such product is STRUKTOL(copyright) TR016.
The ethylene-propylene copolymer, plastomer, filler and any optional additives may be combined and blended using conventional procedures. The blends may be used as such; however, in a highly useful and preferred embodiment of the invention the blends are visbroken. Visbreaking is the controlled degradation of the propylene polymers using chemical and/or thermal means to increase the MFR and improve processability. Visbreaking procedures are described in U.S. Pat. Nos. 3,144,436; 3,940,379 and 4,061,694 which are incorporated herein by reference.
Both chemical and thermal visbreaking involve working the blend containing all of the components at an elevated temperature in a suitable mixer which imparts shear. Single or twin screw extruders, Banbury mixers and the like are commonly used. The operations are typically carried out until the desired melt flow rate is achieved. In batch operations, for example, the operation will be carried out for a period of time sufficient to effect the desired melt flow rate increase. In continuous operations such as where extruders are used to bring about the visbreaking, residence times can be varied or multiple passes can be made.
Thermal visbreaking is generally carried out at temperatures in excess of about 550xc2x0 F. in the absence of free radical initiators. For chemical visbreaking about 50 up to about 2000 ppm free radical initiator, such as a peroxide, hydroperoxide, azo or diazo compound, is included with the polymer. Chemical visbreaking is carried out at a temperature above the melt point of the polymer and above the decomposition temperature of the initiator, typically from about 350xc2x0 F. to 550xc2x0 F.
Visbreaking is advantageously performed on impact copolymer/plastomer/filler blends whose MFR, as a result of the types and/or amounts of the particular components used, is less than 20 g/10 min. It is even more advantageously used with compositions which upon blending have MFRs less than 15 g/10 min. MFRs less than 20 g/10 min and particularly less than 15 g/10 min are generally considered to be unsuitable, or marginally suitable, for high output injection molding operations. By visbreaking, however, the MFRs of the blends can be increased to 20 g/min or higher while retaining acceptable impact and dimensional characteristics. The ability to achieve injection molding blends having MFRs from 20 to 60 g/10 min and, more preferably, in the range 25 to 50 g/10 min utilizing a wide variety of impact copolymer and plastomer components, which by themselves in the ratios employed would not yield products having acceptable flow, is highly beneficial.
The following examples illustrate the invention; however, those skilled in the art will recognize numerous variations which are within the spirit of the invention and scope of the claims.
The propylene impact copolymer used was a reactor-made mixture of propylene copolymer. The ethylene content was 8 wt. % and the MFR was 20 g/10 min. The plastomer was an ethylene-octene-1 copolymer (EG8407; DuPont Dow Elastomers) having a density of 0.87 g/cm3 and MI of 30 g/10 min. The talc was HTP Ultra10C from IMI FABI S.p.A having an average particle size of 1.1 microns. All of the blends of the invention and the comparative blends contained STRUKTOL TR016 blending aid/processing agent. STRUKTOL TR016 is a blend of fatty acid metal soap and an amide.
All of the blends were prepared by dry blending all of the components and feeding the mixture to a Berstorff twin screw extruder for visbreaking. The extruder had nine heating zones where the temperature was increased from 350xc2x0 C. in zone 1 to 380xc2x0 C. in zone 9. The die temperature was 400xc2x0 C. Screw speed was 130 rpm. An amount of peroxide calculated to visbreak the blend in a single pass to an MFR of approximately 35 g/10 min was injected into the extruder at the feed zone. The peroxide used was 2,5-dimethyl-2,5-di-(t-butylperoxy) hexane. The amount of peroxide used varied depending on the initial MFR of the blend, ie. the MFR of the combined blend components prior to visbreaking. The resulting visbroken products were pelletized using a conventional underwater pelletizer.
Impact strength of the blends at xe2x88x9230xc2x0 C. were determined using the instrumented impact method of ASTMD 3763 with a Dynatup model 8250. A weight of 75 lb. pounds and speed of 2.2 m/sec were used to determine the total energy and failure mode. A total of 5 specimens were tested. The failure mode was defined as ductile (d) when the specimen deforms plastically before fracturing. The specimen is in one piece after the penetration and the load-displacement curve is symmetric. When the load goes through a maximum on the load-displacement curve and then drops to zero, the mode is defined as ductile-brittle (DB) failure. Brittle (b) failure is defined when the load falls to zero before reaching a maximum on the load-displacement curve and the sample breaks into multiple pieces. The desired types of failures are either completely ductile or a combination of ductile and ductile-brittle.
Coefficient of linear thermal expansion (CLTE) was determined in accordance with ASTM Test Method E 831. Shrinkage data were obtained by injection molding 6xe2x80x3xc3x976xe2x80x3 0.125xe2x80x3 thick plaques. The plaques were removed from the mold and conditioned for 24 hours under ambient conditions. The difference in size of the plaque from the mold dimensions was then determined in each direction (MD and TD). Results are reported as millimeters shrinkage per meter of material (mm/m). Shrinkage on plaques aged at 250xc2x0 F. for one hour was also determined in the same manner.

High flow filled propylene polymer compositions having improved impact and dimensional properties


A shower fixture has a base adapted to be fixed to a wall, connected to a pressurized-water supply, and having a pressurized water outlet. A pair of generally parallel and spaced tubes have inner ends pivotal about an inner horizontal axis on the base and outer ends. At least one of the tubes is internally connected at the base to the outlet so that pressurized water can flow from the supply through the base to the tube. An element joins together the two tubes for joint pivoting. A shower head mounted between the outer ends is pivotal on the tube about an outer horizontal axis and is connected internally at the outer axis to the one tube so that water from the one tube can flow into the head.

The present invention relates to a shower fixture. More particularly this invention concerns such a fixture having a movable and adjustable shower head.
A shower fixture is known, for example from U.S. Pat. No. 2,011,446 of Judell, that has a base adapted to be fixed to a wall, connected to a pressurized-water supply, and having a pressurized water outlet. A normally metal tube has an inner end pivotal about an inner horizontal axis on the base and an outer end. The tube is internally connected at the base to the outlet so that pressurized water can flow from the supply through the base to the tube. A shower head is pivotal on the tube about an otter horizontal axis at the outer end thereof and is connected internally at the outer axis to the one tube so that water from the one tube can flow into the head. The tube is rigid so that the shower head can be swung in an arc. Thus if, as is standard, the base is mounted on an end wall of a tub-shower enclosure, the head cannot be aimed to the side outside the tub.
The system has two main disadvantages. First, the reaction force of the water spraying from the head is often sufficient, at least if the pressure is high, to pivot up the light arm if the head is aimed tangentially of the first axis. The only way to counter this is to make the joints so tight that using the fixture is difficult. Second, the entire arrangement is fairly flimsy so that, if stressed from the side, it is possible to deform or damage it.
Another system shown in U.S. Pat. No. 2,100,186 of Hagiopian has a telescoping horizontal tube arm whose inner end is pivotal about a vertical axis on a wall-mounted base and whose outer end carries a shower head directed perpendicular to the axis of the telescoping tube. Thus the head can be moved in an arc centered on a vertical axis, can be displaced toward and away from the vertical axis by telescoping of the tube, and can be pivoted about the tube axis by twisting of the outer tube part about the tube axis in the inner tube part. This arrangement is somewhat more rigid, but allows the head to be directed outside the shower. In addition the height of the shower head is not variable, making it very difficult for a person to shower without getting his or her hair wet.
It is therefore an object of the present invention to provide an improved shower-head fixture.
Another object is the provision of such an improved shower-head fixture which overcomes the above-given disadvantages, that is robust, yet that allows the head to be set at any desired height or angle, while making it impossible to spray to the side outside the shower enclosure.
A shower fixture has according to the invention a base adapted to be fixed to a wall, connected to a pressurized-water supply, and having a pressurized water outlet. A pair of generally parallel and spaced tubes have inner ends pivotal about an inner horizontal axis on the base and outer ends. At least one of the tubes is internally connected at the base to the outlet so that pressurized water can flow from the supply through the base to the tube. An element joins together the two tubes for joint pivoting. A shower head mounted between the outer ends is pivotal on the tube about an outer horizontal axis and is connected internally at the outer axis to the one tube so that water from the one tube can flow into the head.
The use of two connected tubes with the shower head between them is extremely robust and can withstand substantially more transverse stress than the prior-art systems. In addition it is strong enough to resist movement when the shower is turned on full, so that it will hold position. The shower head, however, can only move in an arc centered on the inner horizontal axis and can only pivot about the outer horizontal axis, so it cannot be set to spray outside the shower enclosure.
The element according to the invention is rigid and U-shaped and extends between the outer ends of the tubes. The head lies between the element and the inner axis. In addition the fixture has a second such shower head spaced along the tubes from the first-mentioned head and pivotal on the tubes about a second outer axis spaced from the first-mentioned outer axis and parallel thereto. The second shower head is provided with means for controlling and completely shutting off water flow through the second head. The first shower head is provided with means for controlling but not completely shutting off water flow through the first head. Thus dribbling from the first or outer shower head will signal to the user to turn off the water at the source when the system is connected via a hose to a tub faucet, as is common. This feature is not needed if the system is connected up permanently to the water supply. The outer portions of the tubes carrying the first head can telescope with inner portions of the tubes carrying the second head. In this case the element is rigid and U-shaped and extends between the outer ends of the tubes.
Each of the tubes in accordance with the invention is formed at its inner end with an eye and the base includes respective pivot pins centered on the inner axis and engaged in the eyes. At least one of the eyes is formed with a radially inwardly open groove communicating in the respective tube with an interior thereof. The base is formed with a pressurizable flow passage open at the pin of the one eye level with the groove. The pin of the one eye is adapted to be connected directly to the pressurized water supply. More particularly the pin of the one eye forms a passage extending from the respective socket to the groove. The base further is formed with a rearwardly open port opening into the socket of the pin of the one eye. The fixture further has according to the invention either a plug fixable in the port or a feed tube fittable in the port. The plug is used when the fixture is surface mounted and connected to an existing faucet, the feed tube when it is plumbed in permanently.
For ease of assembly at least one of the tubes is formed of telescoping inner and outer parts at the respective inner end. A seal ring is provided between the parts and a snap ring engaged in confronting grooves in the parts.
The base according to the invention is provided on the inner axis with a screw bearing axially on one of the eyes and pressing same against the base so that the screw can be tightened to increase friction between the eye and the base. In this system the pin of the one eye is provided with a pair of washers flanking the one eye and rotationally fixed to the base.
Each tube according to the invention is provided at the outer axis with a mounting socket. The sockets are axially directed toward each other and the head has a body with end stems fitted to the sockets and rotatable relative thereto. The head is rotatable through 360xc2x0 about the outer axis. One of the sockets is tubular and forms a passage between the head and the interior of the respective tube. The other socket blocks flow from the respective tube. This reduces the possible leakage sites in the fixture.
The element in accordance with the invention as described above is rigid and U-shaped and extends between the outer ends of the tubes. The tubes are provided at their outer ends with plugs blocking flow out of the outer ends and with screws securing the outer ends, element, and plug together. A separate cover is secured on a concave inner side of the element.
Outer portions of the tubes lie in a plane forming an angle of between 10xc2x0 and 45xc2x0 to a plane formed by inner portions of the tube. In addition the base is of generally triangular section, is formed with throughgoing holes adapted to receive screws securing the base to a wall, and is provided with a removable decorative cover concealing the holes.


Disclosed herein are composition comprising a modified starch and a carrageenan, especially iota-carrageenan, where the compositions are suitable for use in manufacturing soft capsules.

This invention relates to capsules and, more specifically, to soft capsules typically made using a rotary die apparatus. More specifically, it relates to novel compositions that are capable of forming films from which soft capsule shells can be made.
Encapsulation within a soft capsule of a solution or dispersion of a nutritional or pharmaceutical agent in a liquid carrier offers many advantages over other dosage forms such as compressed, coated or uncoated solid tablets or bulk liquid preparations. Encapsulation of a solution or dispersion permits accurate delivery of a unit dose, an advantage which becomes especially important when relatively small amounts of the active ingredient must be delivered, as in the case of certain hormones. Such uniformity is more difficult to achieve via a tableting process wherein solids must be uniformly mixed and compressed, or via incorporation of the total dose of active ingredient into a bulk liquid carrier which must be measured out prior to each oral administration.
Soft capsules, most commonly, soft gelatin capsules, provide a dosage form which is more readily accepted by patients, since the capsules are easy to swallow and need not be flavored in order to mask the unpleasant taste of the active agent. Soft capsules are also more easily transported by patients than bulk liquids, since only the required number of doses need be removed from the package.
Soft encapsulation of drugs further provides the potential to improve the bioavailability of pharmaceutical agents. Active ingredients are rapidly released in liquid form as soon as the gelatin shell ruptures. Complete disintegration of the capsule is not necessary for the active ingredients to become available for absorption, unlike the case of tableted compositions. Also, relatively insoluble active ingredients can be dispersed in a liquid carrier to provide faster absorption.
Traditionally, both soft and hard-shell capsules have been manufactured using mammalian gelatin as the material of choice for producing the capsule envelope. The rotary die process developed by Robert Scherer in 1933 for producing one piece soft capsules utilized the unique properties of gelatin to enable a continuous soft capsule manufacturing process. The inventive, gelatin-free composition disclosed in this patent application is especially useful in the rotary die method of soft capsule manufacture.
Conventional manufacturing of soft capsules using the rotary die process utilizes mammalian gelatin in a process essentially as follows. Dry gelatin granules are combined with water and suitable plasticizers and the combination is then heated under vacuum to form a molten gelatin mass. The gelatin mass is held in its molten state while being formed or cast as films or ribbons on casting wheels or drums. The films or ribbons are fed under a wedge and between rotary encapsulation dies. Within the encapsulation dies, capsules are simultaneously formed from the films or ribbons, filled, cut and sealed. The seals are formed via a combination of pressure and heat as the capsule is filled and cut. Rotary die manufacture of soft gelatin capsules is disclosed in detail in The Theory and Practice of Industrial Pharmacy (Lachman, Lieberman and Kanig, Editors), 3rd Edition, published by Lea and Febiger. A good description of gelatin encapsulation techniques can also be found in WO 98/42294 (PCT/GB98/00830).
Gelatin formulations used to produce films suitable for making capsules within the rotary die process typically contain between 25% to 45% by weight mammalian gelatin. Levels below 25% by weight tend to lead to poor sealing of the capsule. The physical properties of the gelatin film are critical to the economic production of soft capsules. For example, the film must be strong enough to survive manipulation in the encapsulation machine, provide good sealing properties at temperatures below the melting point of the film, evidence rapid dissolution in gastric juices, and have sufficient elasticity to allow for the formation of the capsule. The wholly non-animal composition of the present invention meets all of these requirements without the use of mammalian gelatin, and surprisingly evidences several improved properties.
The composition according to the present invention, like mammalian gelatin, has many properties that favor its use in soft capsule manufacture. One important property of the inventive compositions with respect to the rotary die process is the ability of the compositions to be cast to form films that are mechanically strong and exhibit elasticity sufficient to allow the film to stretch during filling. In other words, the inventive films have dimensional stability, elasticity and strength adequate for use in a continuous commercial process.
Another important and unique property of the inventive compositions is that the films forming the two halves of the capsule will fuse together during the filling and cutting process when subjected to sufficient pressure and elevated temperature. This fusing together relies on a particular property of the films that allows fusion under conditions of elevated temperature, supplied by the injection wedge, and pressure, supplied by the rotary cutting dies. The temperature at which fusion of two opposing films occurs should be below the melting point of the film, i.e., the fusion or sealing temperature is less than the melting point of the film composition. It has proven difficult to find this combination of properties in other polymer systems. Thus, most proposed substitutes for mammalian gelatin have failed due to a lack of one or more of these properties. This is the main reason why mammalian gelatin has been used almost exclusively as the shell forming material in soft capsule manufacture.
The property of fusion temperature being lower than melting temperature is crucial to the sealing of capsules using the continuous rotary die process. If the fusion and melting temperatures are about the same, the film will nearly completely melt as it passes through the wedge and the rotary die. At this temperature, the film loses its structure. As a result, capsules cannot be produced.
Disadvantages of mammalian gelatin includes the cost and continuity of supply. Gelatin has a variety of other drawbacks. For example, bovine sources are somewhat unattractive to individuals that prefer vegetarian food sources. Also, gelatin is prone to cross-linking, either caused by aging or due to reaction with compounds such as aldehydes. Cross-linking reduces the gelatin insoluble in gastric fluids, a generally undesirable quality for soft capsules. Thus, there is a need in the soft capsule industry for a replacement for the gelatin based compositions.
Other hydrocolloids form films but they lack the attributes of mammalian gelatin required to allow their use in the rotary die process. For example, a variety of modified food starches such as those available from Grain Processing Corporation as Pure-Cote(copyright), are low viscosity starches that provide film-forming and adhesive properties. Such starches form clear, flexible films that are fast drying and flavor free. These materials are suitable as binders for seasonings on snacks and cereals and as smooth, glassy coating agents for confections and baked goods. However, these materials are unable to form hydrated films with the requisite strength and elasticity required for use in the rotary die process. Further, films made entirely from starch have insufficient elasticity and strength to be transferred from the casting drum to the rotary dies. Also, the films adhere too tightly to the casting drum, further diminishing transferability. Thus, compositions are needed that mimic the behavior and characteristics of mammalian gelatin while overcoming its shortcomings.
Japanese Patent Application Kokai Publication No. 63-164858 discloses a composition for the outer skin of soft capsules that allows the filling of hydrophilic materials into the capsule. The composition is a mixture of at least one natural polysaccharide selected from alginic acid, alginic acid derivatives, agar, locust bean gum, carrageenan, guaic gum, tamarind seed polysaccharide, pectin, xanthan gum, glucomannan, chitin, pluran, and cyclodextrin; and at least one substance selected from polyvalent alcohols, sugar alcohols, monosaccharides, disaccharides, and oligosaccharides. The oligosaccharides are described as enzyme and acid decomposition products of sweet potato, potato, corn and the like. While carrageenan is disclosed, there is no distinction made between the various forms of carrageenan (i.e., iota versus kappa). Further, there is no suggestion that the combination of two gelling agents, iota-carrageenan and a modified starch having a hydration temperature below about 90xc2x0 C. would advantageously produce a soft capsule having outstanding physical properties. Further, there is no disclosure or suggestion that a weight ratio of modified starch to iota-carrageenan of at least 1.5:1 is required to produce a film that can be used in a rotary die encapsulation machine to make soft capsules.
International Patent Application No. PCT/FR98/01744 (WO 97/07347) discloses a composition for the manufacture of soft and hard capsules that uses iota-carrageenan as the only gelling agent at concentrations of greater than 5% by weight. This reference does disclose the use of starches and surfactants in the composition at levels of up to 20% by weight for the purpose of accelerating the disintegration of the capsule after contacting gastric juices. No specific teaching on the type of starch is given, other than substances such as wheat, rice, maize or manioc starch which may or many not have been modified, may be used. This reference fails to suggest or disclose the use of gelling starches and iota-carrageenan at weight ratios of at least 1.5:1 to form films useful in making soft capsules, wherein the starch is a modified starch with a hydration temperature of less than 90xc2x0 C.
U.S. Pat. No. 5,342,626 to Winston et al. discloses a composition comprising gellan, carrageenan and mannan gums for producing soft capsules. This patent further discloses that the tri blend of gums can be combined with additional ingredients to form a film-forming polymer composition. This reference, however, fails to disclose the benefits that can be arrived at through the use of iota-carrageenan with certain modified starches.
Japanese Patent Application No. HEI9-25228 discloses a soft capsule film having as essential components agar and water-soluble high polymers, such as the carrageenans. This reference fails to suggest or disclose the combination of iota-carrageenan with a modified starch having a hydration temperature below about 90xc2x0 C. to form films that have outstanding properties in the preparation of soft capsules.
In similar fashion, Japanese Patent Application Disclosure No. HEI5-310529 discloses a capsule forming film comprising agar and carrageenan. The reference points out that kappa carrageenan was found to be preferable. This reference does not make any mention of modified starches being incorporated into the film forming composition.
Japanese Public Patent Disclosure Bulletin No. 61-10508 discloses capsules made from polysaccharides which contain carrageenan and a base which contains multivalent alcohols. The multivalent alcohols include sorbitol, ethylene glycol, glycol, glycerin and the like. No mention is made of iota-carrageenan nor of modified starches.
Another reference suggesting the use of kappa-carrageenan to form capsules is seen in Japanese Patent Application Disclosure No. SHO60-12943. This reference teaches the exclusive use of kappa carrageenan in concentrations of about 1 to about 12% by weight. This reference also suggests that suitable plasticizers or gelatins can be included for increasing film strength.
PCT Application WO 00/10538 to Banner Pharmacaps discloses a gelatin free capsule comprising:
a) 8-50% by weight of a water dispersible or water-soluble plasticizer;
b) 0.5-12% by weight kappa carrageenan;
c) 0-60% by weight dextrins; and
d) 1-95% by weight water
wherein the kappa carrageenan comprises at least 50% by weight of all gums forming or contributing to formation of thermo-reversible gels in the composition. This application does not suggest the combination of a film-forming starch and iota-carrageenan to produce a film of exceptional properties for the formation of soft capsules.
U.S. Pat. No. 5,089,307 to Ninomiya et al. discloses a heat sealable, edible film comprising a film layer consisting essentially of: 1) a water soluble polysaccharide composed chiefly of carrageenan; 2) a polyhydric alcohol; and 3) water. The film of this patent has a water content of not greater than 25% by weight and a weight ratio of the polyhydric alcohol to the water soluble polysaccharide being in the range from 1:5 to 1:1. While this reference does mention all three (3) forms of carrageenan, kappa, iota and lambda, it fails to suggest or disclose a soft capsule formulation containing iota-carrageenan and a modified starch, such as hydroxypropylated tapioca starch.
U.S. Pat. No. 5,817,323 to Hutchison et al. discloses a composition for use in the shell of a comestible capsule comprising gelatin and a plasticizer, such as glycerol, together with a further compound which forms a secondary matrix for the plasticizer. This further component is disclosed as typically being unbleached potato starch acetate. This patent makes no suggestion or disclosure of the use of iota-carrageenan as an elasticizing agent for the film forming modified starches.
U.S. Pat. No. 4,804,542 to Fischer et al. describes gelatin capsules comprising a capsule sheath and a filling wherein the sheath contains a gelatin and at least 1% by weight of an agent selected from the group consisting of starches, starch derivatives, celluloses, cellulose derivatives, milk powder, non-hygroscopic mono-, di- and oligo saccharides, magnesium trisilicate and silicon dioxide. These agents are described as being capable of absorbing water in an amount of at least 10% by weight of its own weight. This patent teaches that the capsule sheath can then be used in containing water miscible, water soluble, water sensitive or hydrophilic materials. This patent makes no mention of iota-carrageenan.
U.S. Pat. No. 3,865,603 to Szymanski et al. relates to modified starch-extended gelatin compositions. This patent discloses modified starches with hydration temperatures above 99xc2x0 C. for use with mammalian gelatin at weight ratios of about 1:9 to 1:1 (starch to gelatin). No mention is made of iota-carrageenan or the special need for soft capsule manufacture with sealing temperatures substantially below the melting point of the film.
The present invention provides compositions for manufacturing capsules, in particular, soft capsules, and especially soft capsules manufactured using the rotary die encapsulation apparatus. The invention provides compositions that do not employ mammalian gelatin and, therefore, overcome the disadvantages associated with collagen-derived material. Compositions of the invention do not contain any significant amounts of gelatin but, instead, require at least two (2) agents: 1) a modified starch having a hydration temperature below about 90xc2x0 C. and 2) iota-carrageenan.
As those skilled in the art of soft capsule manufacture will appreciate, the film formed on the drum of the encapsulation machine is called the xe2x80x9cwet filmxe2x80x9d. This film is used in the rotary encapsulation machine to form the filled capsules. The capsules are then dried using any number of techniques. During the drying process, water is removed from the fill material (when the fill material is hydrophilic) and the capsule shell. The result is a soft capsule with a xe2x80x9cdry filmxe2x80x9d. The dry film comprises the various components, i.e., carrageenan, plasticizer, modified starch and the like and xe2x80x9cbound waterxe2x80x9d. The bound water, from about 6 to 12% by weight of the dry film, is not easily removable using conventional drying techniques and is not considered when describing the components of the dried film as a percentage of the composition. The dried film numbers are calculated numbers based upon a assumed weight percent of the bound water.
Thus, for example, Table I sets out the components of the inventive film forming composition and representative weight percent ranges for the wet film and the dry film.
As will be demonstrated in the Examples, one aspect of the present invention resides in the discovery that the weight ratio of the modified starch to the iota-carrageenan is crucial to forming a satisfactory film. The weight ratio of the modified starch to the iota-carrageenan is at least 1.5:1, with a preferred range being 1.5:1 to 4:1. Another feature useful in characterizing the inventive film is fusion pressure. The mixture of modified starch, iota-carrageenan and other components should result in a wet film that fuses at pressures above 207 kPa.
Thus, there is disclosed, a composition suitable for forming a film for encapsulating materials, the composition comprising a modified starch and iota-carrageenan in a ratio by weight of at least 1.5:1; said film capable of fusion under a pressure of at least about 207 kPa (30 psi). There is further disclosed a composition wherein the weight ratio of modified starch to iota-carrageenan ranges from 1.5:1 to 4:1, more preferably from 2:1 to 3:1. Further, the invention relates to a film forming composition that is capable of fusion, under pressure, in the range of 207 kPa to 2070 kPa (30 to 300 psi) and at temperatures in the range of from 25-80xc2x0 C. In a yet more preferred embodiment, the film according to the present invention has a melting temperature of from 2 to 25xc2x0 C., more preferably 3-15xc2x0 C. and most preferably 4-9xc2x0 C. above its fusion temperature.
More specifically, the compositions according to the invention (expressed as wet film) comprise from 5-50% by weight modified starch; more preferably 15-40% by weight and the preferred modified starch is hydroxypropylated acid modified corn starch. The invention is also most preferably a composition wherein iota-carrageenan comprises at least 6 and up to 12% by weight of the composition. The composition according to the present invention may also contain a plasticizer such as glycerin and the plasticizer may comprise up to 50% by weight of the composition, more preferably up to 30% by weight.
There is also disclosed a dried film composition for soft capsules, the composition consisting essentially of from 42-84% by weight gel formers comprising a mixture of iota-carrageenan and modified starch; a plasticizer; and a buffer.
There is further disclosed a composition suitable for forming a soft capsule, the composition comprising iota-carrageenan and at least one modified starch selected from the group consisting of hydroxypropylated tapioca starch, hydroxypropylated maize starch, acid thinned hydroxypropylated corn starch, potato starch, pregelatinized modified corn starches, and wherein said starch has a hydration temperature below about 90xc2x0 C. and wherein the weight ratio of modified starch to iota-carrageenan ranges from 1.5:1 to 4.0:1. The invention also relates to a soft capsule comprising a shell and a fill material wherein the shell is a film according to the present invention.
In general, the invention provides compositions that function effectively as replacements for the conventional mammalian gelatin based compositions. Thus, the compositions of the invention possess many of the desirable important characteristics of gelatin. The inventive compositions form films that are mechanically strong and exhibit elasticity sufficient to allow the film to stretch during filling (blow-molding). Thus, the invention films have dimensional stability, elasticity and strength adequate for use in a continuous process which requires their removal from a casting drum and subsequent transport to rotary dies. Unexpectedly, the fusion or sealing temperature is substantially less than the melting point of the inventive film. Thus, films formed from the compositions of the invention simultaneously fuse together during the filling and cutting portion of the rotary die process when subjected to sufficient pressure and elevated temperature.
An additional unexpected property of the films according to the invention is that sealing occurs at substantially lower pressures than those experienced with mammalian gelatin based compositions. For example, conventional mammalian gelatin based films seal at pressures of about 1,724 kPa (250 psi) whereas the new films according to the present invention seal at about 207 kpa, more preferably about 552 kPa (30-80 psi). This saves energy and reduces the wear experienced by the rotary die. Also, the inventive film, when dry, (the film contains about 6 to 12% by weight water) is durable and impermeable to hydrophobic liquids.
As used herein and in the claims, the term xe2x80x9cfusionxe2x80x9d is meant to mean the welding of two (2) films by the use of pressure so as to result in a bond that is not easily separated. The fusion of the two films during the rotary die process results in a seal that is adequate to hold the liquid fill of the soft capsule during its anticipated shelf life.
In a preferred embodiment, the invention provides compositions comprising at least one modified starch and iota-carrageenan in a ratio by weight in the range of 1.5:1 to 4:1; plasticizers; buffers and optionally preservatives. Such materials can be formed into films that have sufficient structure, elasticity and strength to be removed from a temperature-controlled casting surface. It has unexpectedly been found that a combination of carrageenan, especially iota-carrageenan, and at least one modified starch, forms films having characteristics that allow the film to be reversibly stretched during the capsule filling step. These compositions, as wet films, preferably comprise water, 6-12 weight % iota-carrageenan, 12-30 weight % modified starch, 5-30 weight % plasticizers, 0.5-2 weight % buffers and optionally 0-0.2 weight % preservatives.
In another embodiment, the invention provides films comprising water and a solids system. In the films of the present invention, the solids system comprises modified starch and iota-carrageenan. The films of the invention are capable of maintaining their form without being applied to a support; they do not lose their shape through splitting, lengthening, disintegration or otherwise by breakdown of the film when unsupported. However, the films may be stretched when pulled or compressed to a certain extent when an appropriate external force is applied.
As used herein and in the claims, the term xe2x80x9cmodified starchxe2x80x9d includes such starches as hydroxypropylated starches, acid thinned starches and the like. The only native starch determined to be functional with iota-carrageenan in preparing the films according to the invention is potato starch, thereby the term xe2x80x9cmodified starchxe2x80x9d is meant to include native, unmodified potato starch. In general, modified starches are products prepared by chemical treatment of starches, for example, acid treatment starches, enzyme treatment starches, oxidized starches, cross-bonding starches, and other starch derivatives. It is preferred that the modified starches be derivatized wherein side chains are modified with hydrophilic or hydrophobic groups to thereby form a more complicated structure with a strong interaction between side chains.
Through the diligent work of the inventors herein, they have determined that some starches are barely functional in their inventive compositions and include high amylose starches, native starches other than potato starch and cross-linked starches. Hydrogenated starch hydrolysates that have been used to promote the disintegration of the gelatin capsule would likewise not be useful in the present invention.
There are two characteristics that help characterize modified starches that are useful in the present invention and they are 1) hydration temperatures below about 90xc2x0 C. and 2) film forming capabilities. Through a careful study of numerous starches, it has been determined that the following starches are not useful in the present invention: tapioca dextrin, high amylose non-modified corn starch, modified waxy maize starch, non-granular starch, modified high amylose corn starch and pregelatinized rice flour.
There is further disclosed an edible, soft capsule which comprises:
a) a soft, dry shell which comprises:
(i) about 12-24 weight % iota-carrageenan;
(ii) about 30-60 weight % modified starch;
(iii) about 10-60 weight % plasticizer;
(iv) about 1-4 weight % sodium phosphate dibasic buffer system; and
wherein said shell encloses:
b) a soft capsule fill material.
In a further embodiment of the invention, there is disclosed a capsule wherein the plasticizer is comprised of glycerin or sorbitol or a mixture thereof and the modified starch is selected from modified corn starch, acid modified hydroxypropylated corn starch and hydroxypropylated acid modified tapioca starch.
Carrageenan has been known for decades as a useful food ingredient. While salt and sugar are rather simple food ingredients, technologically, carrageenans are rather complex and there are hundreds of different products available in the market called carrageenan with highly different price levels and functionalities. Carrageenan is obtained by aqueous extraction of natural strains of seaweeds of Gigartinaceae, Solieriaceae, Phyllophoraceae, and Hypneaceae, families of the class Rhodophyceae (red seaweeds). The three major forms of carrageenan are known as iota, kappa and lambda carrageenan. Lambda and kappa carrageenans do not typically occur together in the same plant, however, since the various species are harvested together, extraction yields a typical mixture of kappa and lambda with an average of around 70% kappa and 30% lambda. Euchema Spinosum is the seaweed source for production of iota-carrageenan either as an extract or as a processed Euchema seaweed. During the production of carrageenans, it is common that no sorting takes place before shipment of the seaweed to the carrageenan rendering facilities. Seaweeds are typically sold based on seaweed type and content of sand, salt, stones and humidity and not based on functional specifications. Thus, carrageenan manufacturers need to test each seaweed shipment to determine the quality of the extractable carrageenan in order to see if any processing adjustments are needed for obtaining the desired specifications. Carrageenans are available in the market place as standardized and non-standardized carrageenans. Standardization is done either by blending different pure carrageenan batches (cross-blending) or by blending one or more carrageenan batches with other ingredients such as salts (KCl, NaCl, and CaCl2) and/or sugars (saccharose, dextrose, maltodextrins, lactose) in order to reach the desired specification. As used herein an in the claims, the recited weight percents for iota-carrageenan include the standardizing ingredient.
All carrageenans are water soluble gums having the common structural feature of being linear polysaccharides with a sugar backbone of alternating units consisting of galactose units linked by 1,3-xcex2-D-linkages, as well as 1,4-xcex1-D-linkages. The fundamental properties of iota, kappa and lambda are a function of the number and position of the ester sulfate groups. Iota-carrageenan contains approximately 30% by weight 3,6 anhydro-D-galactose and 32% ester sulfate by weight. In contrast, kappa carrageenan contains more than 36% by weight 3,6 anhydro-D-galactose and 32% ester sulfate by weight. Molecular weight ranges from 100,000 to 500,000 Daltons. The gelling carrageenans (kappa and iota) contain an xe2x80x9cinternalxe2x80x9d ringxe2x80x94the 3,6-anhydro ring. The presence of ester sulfate makes carrageenans negatively charged at all pH values and is responsible for carrageenans being highly reactive molecules. Commercially available carrageenans are typically not well defined chemical compounds. However, through careful quality control, relatively pure materials with specified properties are available commercially.
The gelling carrageenan types (kappa and iota) are biosynthesized by the living seaweed as a non-gelling precursor, which is then turned into the gelling form by the action of the enzyme, dekinkase, which catalyzes the formation of the 3,6-anhydroglacatose ring. As mentioned previously, iota-carrageenan is only produced from Euchema Spinosum and produces the strongest gels with calcium ions (Ca++). The gels are very elastic and completely syneresis free at the normal concentrations for food application (i.e., 0.5 to 2% by weight). Although iota-carrageenan does not gel with Na+, diluted iota-carrageenan solutions will form thixotropic solutions also with Na+ as it acts as a stabilizing agent. In the best mode of the present invention, the Ca++ content is kept to a minimum.
In iota-carrageenan, the 1,3- and 1,4- linked units are respectively D-galactose-4-sulfate and 3,6-anhydro-D-galactose-2-sulfate. However, some of the 3,6-anhydro-D-galactose-2-sulfate rings may be replaced by D-galactose-6-sulfate, which may reduce considerably the gelling power of the iota-carrageenan.
The iota-carrageenans useful in the composition according to the invention should conform to the specification laid down by the USA and European regulatory authorities. The iota-carrageenan should not be degraded and should conform to minimum viscosity standards, which correspond to a molecular weight of about 100K Daltons.
Syneresis is often measured on carrageenan gels to determine breaking force and characterize the iota from the kappa carrageenan. After breaking force has been measured, the gel is transferred to a petri dish and covered to avoid evaporation from the gels. After typically about four (4) hours, the amount of free water (the syneresis) is measured. A high value indicates a strong gelling kappa, whereas no syneresis indicates iota.
Table II sets out typical analytical patterns and values for iota-carrageenan.
Through extensive investigative efforts, the inventors have determined that iota-carrageenan alone does not produce an acceptable film and that the modified starches alone do not produce a useable film for encapsulation. Without being bound to any theory or mechanism, it is speculated that the iota-carrageenan and modified starches interact synergistically to provide films of sufficient strength and elasticity to be useful in the encapsulation process.
The films made from the compositions of the invention possess the desirable properties of the films made from gelatin and function as effective replacements for gelatin films in virtually all processes that employ aqueous-gelatin compositions for the production of soft capsules. Among those processes are rotary die encapsulation processes, reciprocating die encapsulation processes, concentric cylinder processes, and processes for film-enrobing tablets. The film-enrobing process is also a rotary die process, as described in U.S. Pat. No. 5,146,730, the disclosure of which is incorporated herein by reference in its entirety. Thus, the compositions of the present invention provide:
i) mechanically strong, elastic films that set on a temperature-controlled casting drum generally within from about 15 to about 60 seconds, preferably less than about 20 seconds;
ii) films that, when brought into contact with one another, fuse together at temperatures of from about 25-80xc2x0 C. and pressures of from about 207 to about 2070 kPa (30-300 psi);
iii) films that fuse (form seals in the rotary die process) at temperatures significantly below the melting point of the films; and
iv) strong, durable dried films.
Still other advantages of the inventive compositions include:
i) finished capsules are not prone to cross-linking or insolubilization due to interaction with materials such as aldehydes, phenols ketones, that may be present within the capsule fill or shell, or that are formed over time by oxidization; and
ii) finished capsules exhibit greater stability when exposed to elevated humidity and temperature than capsules made using gelatin.
The compositions of the present invention are capable of forming unsupported wet and/or dry films, i.e., the films do not require a support to maintain their shape and structure. Further, they do not disintegrate, tear or fracture unless some significant external force is applied. The compositions of the invention are formed into films by any of a variety of suitable methods. While casting or extruding onto a casting drum is preferred in connection with the rotary die process, other processes for forming films will be apparent to those skilled in the art.
Other components may also be incorporated into the compositions provided they do not alter the melting point/fusion point characteristics of the inventive film. Representative of these additional components include flavoring agents, opacifying agents, preservatives, embrittlement inhibiting agents, colorants and disintegrants. The inventive compositions are typically in the molten state when these components are added. Use of conventional pharmaceutical or food grade ingredients is acceptable.
As used herein and in the claims, the phrase xe2x80x9can amount of modified starch effective to form a structured filmxe2x80x9d means an amount of a modified starch sufficient to form a film or gel that does not flow, but has dimensional stability. More preferably, the phrase xe2x80x9ceffective to form a structured filmxe2x80x9d means an amount of a modified starch sufficient to form a dimensionally stable film having a thickness of at least about 0.01 inches.
The phrase xe2x80x9ceffective elasticizing amountxe2x80x9d means an amount of iota-carrageenan sufficient to provide a starch based composition in the form of film with sufficient strength to be removed from a casting drug during rotary die processing and also sufficient elasticity to be deformed during the rotary die process when a fill material is presented between a pair of films of the composition (blow molded).
The phrase xe2x80x9cfusion temperaturexe2x80x9d means the temperature at which two opposing films, in contact with each other, will blend at their contact interface to become one, indistinguishable and inseparable structure.
The weight ratio of modified starch to iota-carrageenan in this invention is at least 1.5:1, more preferably from about 1.5:1 to about 4:1, most preferably, from about 2:1 to about 3:1. Unexpectedly, the compositions of the invention possess the important characteristic of having a melting point temperature that is substantially higher than the fusion temperature. Preferably, the melting point temperature of a film according to the invention, is from about 3-15xc2x0 C., and more preferably from about 4 to 9xc2x0 C., above its fusion temperature.
While not being bound to any theory or mechanism, it is believed that the iota-carrageenan functions as an elasticizing agent. In other words, this elasticizing agent renders an otherwise in-elastic, modified starch film, elastic. Consequently, the films of the invention have a xe2x80x9cmemoryxe2x80x9d and are capable of returning substantially to their original size and shape after being subjected to a deforming force. For example, a film made from the starch/carrageenan compositions of the invention that is stretched along its length and/or width will substantially return to its original length over time.
As discussed previously, the modified starches useful in the present invention include those starches that have a hydration temperature below about 90xc2x0 C. Hydration temperatures for most starches are available in the literature, such as product data for commercially available starches. Where they are not available via the literature, such hydration temperatures may be readily determined employing techniques well know to those skilled in the art. Suitable starches also must be capable of forming an aqueous mixture with water at a concentration of at least from about 20 weight % to give a mixture having a viscosity below about 60,000 to 80,000 centipoise (cps) measured at a 10 sec-1 shear rate at the temperature at which starch hydration occurs.
Representative of the commercially available starches useful in the present invention include Pure Cote(trademark) B760 and B790 (an acid-modified hydroxypropylated corn starch), Pure-Cote(trademark) B793 (a pre-gelatinized modified corn starch), Pure-Cote(trademark) B795 (a pre-gelatinized modified corn starch) and Pure-Set(trademark) B965 (a flash-dried acid modified native corn dent starch), all available from the Grain Processing Corporation of Muscatine, Iowa. Other useful, commercially available, modified starches include C*AraTex(trademark) 75701 (hydroxypropylated acid modified tapioca starch), available from Cerestar, Inc. of Hammond, Ind.; M250 and M180 (maltrins) and Pure-Dent(trademark) B890 (modified corn starch) from Grain Processing Corporation; and Midsol Crisp (modified high amylose corn starch) from Midwest Grain, Inc. of Atkinson, Kans. The only native (unmodified) starch suitable for use herein is potato starch. Such a starch is available from Roquette as Potato Starch Supra Bacter.
The invention may include genetically (recombinantly) modified and hybridized starches. Genetically modified and hybridized starches include those that have been developed to alter the physical properties and/or the amylose/amylopectin ratios. The preferred starch is an acid hydrolyzed corn starch modified with 2-hydroxypropyl ether functional groups. This starch is identified by Chemical Abstracts Service Registry No.68584-86-1. This material is commercially available as PURE-COTE(trademark) B760 and B790 from Grain Processing Corporation.
The iota-carrageenan is present in the inventive compositions in an amount that, in combination with starch, effectively causes the compositions to have the required gelatin-like functional properties. As discussed previously, as those skilled in the art will appreciate, the film has what is known as a wet shell composition and a dry shell composition. This results from the evaporation of water from the film during the manufacturing process of the soft capsule. Preferred amounts of iota-carrageenan range from about 6 to 12% by weight of the wet shell composition. More preferred amounts of iota-carrageenan range from about 7-12% by weight of the wet composition. Particularly preferred compositions contain from about 9-11 weight % of iota-carrageenan, based on the weight of the wet composition. Even more preferred compositions contain about 10 weight % of iota-carrageenan by weight of the wet composition.
As will be demonstrated in the Examples, not all members of the carrageenans family can be used herein. Standardized iota-carrageenans are preferred. A particular preferred standardized iota-carrageenan is commercial available from the FMC Corporation of Princeton, N.J., known as VISCARIN(copyright) SD389, standardized with 15% by weight dextrose. Other useful iota-carrageenans include a non-standardized iota-carrageenan from SKW BioSystems of Baupt, France known as XPU-HGI and a non-standardized iota-carrageenan from FMC.
In general, the film forming compositions may consist of the iota-carrageenan, at least one modified starch with the balance of the composition being water. However, preferred compositions of the invention include a plasticizer. Suitable plasticizers include the materials used for the same purpose in the manufacture of mammalian gelatin capsules. Representative plasticizers are any of a variety of polyhydric alcohols such as glycerin, sorbitol, propylene glycol, polyethylene glycol and the like. Other plasticizers include saccharides and polysaccharides. The saccharides and polysaccharides suitable for use herein may be produced by hydrolysis and/or hydrogenation of a simple or complex polysaccharides.
Where plasticizers are employed, they can be used in amounts of up to about 60% by weight of the dry shell composition or 30% of the wet shell composition. More preferred compositions contain from about 10 to 25% by weight, based on the weight of the wet shell composition and 30-50% by weight of the dry shell composition.
Also, the capsule forming composition, i.e., the shell mass composition, may optionally contain an embrittlement inhibiting composition. An example of embrittlement inhibiting compositions is a mixture of sorbitol and one or more sorbitans. See U.S. Pat. No. 4,780,316.
Optionally, the film forming composition may contain preservatives and stabilizers such as mixed parabens, ordinarily methyl or propyl parabens, in about a 4:1 ratio. The parabens may be incorporated in the compositions at levels of 0-0.2 weight % for the wet shell and 0-0.4 weight % for the dry shell. It should be noted that in the following Examples, preservatives were included in the experimental formulation to facilitate un-dried sample retention for later evaluations. Without preservatives, the retained wet ribbons would be spoiled by microbial growth in a day or two. On a commercial scale, preservatives would typically note be added to the film forming composition because the wet ribbon would be quickly processed through the encapsulation machines and then the dryers. The dried film does not support microbial growth.
It has been found by the inventors that the use of a buffer system in the inventive compositions is highly desirable. Any known buffer can be used with phosphate buffers being preferred. Controlling the pH of the melt and film is highly important as carrageenans are rapidly broken down in conditions of high temperature and acidity. As mentioned previously, the presence of Ca++ ions should be kept to a minimum.
Soft capsules may be manufactured in accordance with conventional techniques as set forth in Ebert, W. R., xe2x80x9cSoft elastic gelatin capsules: a unique dosage formxe2x80x9d, Pharmaceutical Tech., October 1977; Stanley, J. P., xe2x80x9cSoft Gelatin Capsulesxe2x80x9d, in The Theory and Practice of Industrial Pharmacy, 359-84 (Lea and Febiger ed. 1970); U.S. Pat. Nos. 1,970,396; 2,288,327; and 2,318,718.
The capsules made using the rotary die process, will typically have wet shell thicknesses varying from about 0.024 to 0.1778, preferably from about 0.0508 to 0.127 and more preferably from about 0.0508 to 0.0762 cm in thickness. The capsules of the invention may be manufactured in any desired shape using the above-mentioned rotary die process.
The fill materials for the soft capsules may be any of a wide variety of materials suitable for encapsulation using the rotary die apparatus. Among the types of materials that are suitable for encapsulation include oils, hydrophilic liquids and emulsions. The active components that may be contained within the oils and emulsions are hydrophobic and hydrophilic actives. Those skilled in the art are familiar with and will recognize suitable fill materials. These fill materials may contain cosmetics, foods including vitamins, liquids, semi-solids, suspensions, flavorings and pharmaceuticals. After filling, the capsules are typically dried according to conventional techniques, e.g., tray drying, using a drum dryer or other suitable drying methods.

Film forming compositions comprising modified starches and iota-carrageenan and methods for manufacturing soft capsules using same